The present invention is related to detecting window contamination, in general, and more particular to a method and apparatus for detecting contaminants on a window surface of a viewing system utilizing light.
A windowed area is generally used to protect a viewer or viewing system from the environment of a viewing scene. Contaminants which may be particulates, such as dust, ice, water and the like, for example, may form on the outside window surface and obscure the view of the scene. A viewer can detect such contaminants and move his or her head to view the scene from a different perspective, thus avoiding the contaminants. However, in viewing systems, a camera may be located at a stationary position behind the window to view a scene through the window from a fixed perspective. Under these circumstances, any contaminants formed on the window in the viewing area of the camera will degrade the image produced by the camera.
Viewing systems which utilize automated image processing for a particular application are particularly vulnerable to contaminants forming on the viewing area of the window surface. Such systems may view the scene through a video or infrared camera, for example, which produce electrical signals representative of image frames of the scene. Each frame may be comprised of rows and columns of picture elements or pixels. Each electrical signal may be representative of the light intensity of each picture element of the frame. A signal processor may be used to process the pixel signals of each image frame to detect a change in a parameter viewed in the scene according to some predetermined criteria. If the camera images are not displayed to a person, contaminants formed in the viewing area of the window will go undetected. Such contaminants may affect the pixel signals and cause a false detection of a parameter change. Accordingly, decisions made by the image processing of the pixel signals will be compromised by the contaminants.
The present invention provides for a method and apparatus for detecting contaminants in the viewing area of the window surface utilizing light so that an operator may be made aware of such contaminants and a potential compromise of the decisions made by image processing of the pixel signals.